This invention relates generally to coding systems, and more particularly to an encoded label for a magnetic tape cartridge.
In the field of machine-readable codes, the bar code is one of the most widely used and recognized forms of machine-readable codes since it is utilized on numerous commercial articles and other applications. One bar code in particular, the universal product code (UPC), has gained widespread acceptance. The UPC numbering system as described in the "UPC Symbol Specification" published by the Uniform Product Code Council, Inc., Dayton, Ohio, is primarily designed for such ten-digit codes, but also includes growth capacity for longer codes (e.g., 11 and 12 characters) to facilitate compatibility in all distribution industries in the future. The symbol even provides a format capable of encoding 13 to 30 characters to promote compatibility with the needs of department stores.
The standard symbol (a machine-readable version of the UPC and other compatible codes) is in the form of a series of parallel light and dark bars of different widths, and an OCR-A or B numeric font equivalent which hereinafter will be referred to as the "bar code symbol." However, such a bar code symbol is not to be confused with the UPC, which is the numbering system that is represented by the symbol.
As is conventional, the basic characteristics of the UPC symbol are as follows. For any ten-character code, the symbol consists of a series of thirty dark and 29 light parallel bars with a light margin on each side, each character of digit of a code being represented by two dark bars and two light spaces. The overall shape of the code is rectangular in nature, with each character being independent. A character is typically made up of seven data elements or "modules" which may be light or dark, and a bar may be made up of from one to four dark modules.
The symbol also includes two characters beyond the ten needed to encode the UPC. One character, a module check character, is embedded in the right-most position of the symbol to ensure a high level of reading reliability. Another character, embedded in the left-most position of the symbol, shows which number system a particular symbol encodes. Concurrent number sets are typically used to accommodate such things as "meat" and "produce" without the need to set aside code numbers in the UPC.
Symbol size is infinitely variable in order to accommodate the ranges in quality achievable by various printing processes. That is, the size of the symbol can be uniformly magnified or reduced from a nominal size without significantly affecting the degree to which it can be scanned. Most applications are "wandable," which means that a simple handheld device can be used to scan or read the symbol, but fixed-position scanners can also be built to scan the symbol in an omnidirectional manner. That is, devices are known which automatically read the symbol when it is drawn past the scanner i any orientation.
The conventional symbol is also capable of preventing tampering. That is, unauthorized additions of lines to the preprinted symbol is readily detectable by conventional scanning devices. In the same way, poor printing will not result in the scanning devices reading a wrong number. This is facilitated since the symbol has multiple error-detecting features which allow scanner designers to build equipment to automatically detect and reject a very poorly printed symbol, or one that has been tampered with. Such symbols also incorporate and present the code number in a human-readable form. Further details relating to the UPC may be found in the aforementioned "UPC Symbol Specification" which is incorporated herein by reference.
Many other forms of bar codes exist in the prior art. For example, the Code 39 or "3 of 9" bar code (as described in the American National Standards Institute publication ANSI MH10.8M-1983, also incorporated herein by reference) and the interleaved 2 of 5 code have achieved equally widespread application. Such codes, like the UPC, consist of a plurality of light and dark parallel bars variously arranged to encode information with features to prevent tampering and account for poorly printed symbols. The 3 to 9 bar code also is capable of encoding alphabetical characters as well as numerical characters.
One problem each of the above described codes face when combined in systems using automatic scanners (such as the 4400 Automated Cartridge System manufactured by the Storage Technology Corporation), however, is how to reliably read codes which may have significant portions of their information missing. As described in U.S. patent application Ser. No. 007,047, filed Jan. 27, 1987, assigned to the assignee of the present invention and incorporated herein by reference, the 4400 Automated Cartridge System comprises a fully-automated, 18-track cartridge-based storage and retrieval system which includes at least one library storage module consisting of a housing, a plurality of cartridge storage cells arranged in a pair of concentric arrays contained within the housing, an optical system that identifies selected ones of the plurality of cartridges, and an electromechanical system or "robot" that picks up the selected cartridge, delivers it to an associated tape transport for reading data therefrom or writing data thereto, retrieves the cartridge upon completion of the reading/writing operation, and returns it to its appropriate storage cell. An attached library control unit contains the electronics necessary to control the robot's movement within the library storage module.
In order to permit the robot to carry out its assigned functions, a label having a machine-readable code must be affixed to each of the cartridges stored within the library storage module. Most prior art labels for such cartridges are merely comprised of a human-readable code (i.e., a plurality of numbers and perhaps a plurality of colors, each of which are associated with a respective number). However, one prior art label which incorporates both a machine-readable code and a human-readable code is manufactured by Wright Line Inc. of Worcester, Mass.
The Wright Line label, as is known, consists of a one-piece, pre-printed coded label having at least two identical messages. A first message is arranged in a first column on the label in which there is printed a series of data characters of an optical character recognition (OCR) format. The data characters, thus, form a message in a first code which is both machine-readable and human-readable. A second column, contiguous with the first column and coextensive therewith, contains a single machine-readable bar code symbol comprising a message in a second code which corresponds to the first message, but which is intentionally printed to be readable in a direction opposite to the direction of scan for the first message. In such a manner, the Wright Line label is said to obviate problematic situations in which a portion of the label was missing obliterated.
It is apparent from the above, however, that the mere reversing of the redundant codes would not provide the requisite machine-readability for applications such as in the 4400 Automated Cartridge System when a substantial portion of the label was missing or obliterated. For example, if the central portion of the Wright Line label was entirely missing from the cartridge, the same central portion of the at least two redundant codes would be unavailable for scan by the optical system. That is, assuming for purposes of illustration that the cartridge to be identified by the Wright Line label was designated "123456," and the central portion of the label was missing of obliterated, the encoded "34" portion of the label would be unavailable for scan by the optical system whether read as "34" or "43". It would, therefore, be desirable to provide an improved encoded label for a magnetic tape cartridge which would not be susceptible to such problems.